/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    Arithmetic.java
 *    Copyright (C) 2008 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core.pmml;

import java.util.ArrayList;

import weka.core.Attribute;

/**
 * Built-in function for +, -, *, /.
 * 
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
 * @version $Revision 1.0 $
 */
public class BuiltInArithmetic extends Function {

	/**
	 * For serialization.
	 */
	private static final long serialVersionUID = 2275009453597279459L;

	/**
	 * Enumerated type for the operator.
	 */
	enum Operator {
		ADDITION(" + ") {
			double eval(double a, double b) {
				return a + b;
			}
		},
		SUBTRACTION(" - ") {
			double eval(double a, double b) {
				return a - b;
			}
		},
		MULTIPLICATION(" * ") {
			double eval(double a, double b) {
				return a * b;
			}
		},
		DIVISION(" / ") {
			double eval(double a, double b) {
				return a / b;
			}
		};

		abstract double eval(double a, double b);

		private final String m_stringVal;

		Operator(String opName) {
			m_stringVal = opName;
		}

		public String toString() {
			return m_stringVal;
		}
	}

	/** The operator for this function */
	protected Operator m_operator = Operator.ADDITION;

	/**
	 * Construct a new Arithmetic built-in pmml function.
	 * 
	 * @param op
	 *            the operator to use.
	 */
	public BuiltInArithmetic(Operator op) {
		m_operator = op;
		m_functionName = m_operator.toString();
	}

	/**
	 * Set the structure of the parameters that are expected as input by this
	 * function. This must be called before getOutputDef() is called.
	 * 
	 * @param paramDefs
	 *            the structure of the input parameters
	 * @throws Exception
	 *             if the number or types of parameters are not acceptable by
	 *             this function
	 */
	public void setParameterDefs(ArrayList<Attribute> paramDefs)
			throws Exception {
		m_parameterDefs = paramDefs;

		if (m_parameterDefs.size() != 2) {
			throw new Exception(
					"[Arithmetic] wrong number of parameters. Recieved "
							+ m_parameterDefs.size() + ", expected 2.");
		}
	}

	/**
	 * Returns an array of the names of the parameters expected as input by this
	 * function
	 * 
	 * @return an array of the parameter names
	 */
	public String[] getParameterNames() {
		String[] result = { "A", "B" };
		return result;
	}

	/**
	 * Get the structure of the result produced by this function. Subclasses
	 * must implement.
	 * 
	 * @return the structure of the result produced by this function.
	 */
	public Attribute getOutputDef() {
		return new Attribute("BuiltInArithmeticResult:" + m_operator.toString());
	}

	/**
	 * Get the result of applying this function.
	 * 
	 * @param incoming
	 *            the arguments to this function (supplied in order to match
	 *            that of the parameter definitions
	 * @return the result of applying this function. When the optype is
	 *         categorical or ordinal, an index into the values of the output
	 *         definition is returned.
	 * @throws Exception
	 *             if there is a problem computing the result of this function
	 */
	public double getResult(double[] incoming) throws Exception {
		if (m_parameterDefs == null) {
			throw new Exception(
					"[BuiltInArithmetic] incoming parameter structure has not been set!");
		}

		if (m_parameterDefs.size() != 2 || incoming.length != 2) {
			throw new Exception(
					"[BuiltInArithmetic] wrong number of parameters!");
		}

		double result = m_operator.eval(incoming[0], incoming[1]);

		return result;
	}

	public String toString() {
		return toString("");
	}

	public String toString(String pad) {
		return pad + m_parameterDefs.get(0).name() + m_functionName
				+ m_parameterDefs.get(1).name();
	}
}